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SciAps leads handheld LIBS applications at SciX 2022

Read below for emerging applications presented at SciX using the world’s leading handheld LIBS, created by the people who helped write the book on portable spectroscopy and spectrometry. Click on our Independent Studies page to explore even more.

SciX, presented by FACSS, is a leading conference for analytical chemists seeking scientific exchange, with a unique blend of technical sessions covering all fields of analytical chemistry, a cutting-edge exhibit floor, and networking opportunities.


Fundamentals

Fundamental Approaches to Broaden the Applications of Commercial Handheld LIBS

Matthieu Baudelet, Kristen Livingston, Magdalena E. Jackson; University of Central Florida, Rensselaer Polytechnic Institute

The calibration-free method has mostly been successfully applied to LIBS (CF-LIBS) in laboratory conditions. However, field analysis is increasingly required for the analysis of 27 several samples where no standards are available (such as anthropology and archaeology). As a result, it is more practical to use a portable, handheld LIBS (hhLIBS) instrument to analyze these materials. This study establishes whether the calibration-free method can be applied to hhLIBS data to successfully measure elemental concentration using CF-LIBS. Demonstrating the ability of calibration-free hhLIBS to serve as an accurate quantitative technique would decrease the need for matrix-matched standards and will broaden the range of analytical applications in fieldwork. Results and also discussion about the fundamental differences between traditional and handheld LIBS plasmas will be the focus on this talk, in order to determine how much broader we can bring quantitive portable LIBS into areas where calibration standards are not available yet.

Chemometrics

Applications of Classification Algorithms to Data from Portable Instrumentation

Caelin Celani, Karl Booksh, Jocelyn Alcantara-Garcia, Tyler Coplen, James Jordan, William Johnston, Amelia Speed, Rachel McCormick, Olivia Jaeger, Carolyn Chen; University of Delaware, United States Geological Survey, Fairmont State University, Army Public Health Center, Noramco, Eurofins PSS Insourcing

Chemometrics applied to various portable instrumentation applications

The advent and growing popularity of handheld instrumentation is allowing for the expansion of the analytical laboratory to locations previously inaccessible. While a primary trade off of having field portability is diminished spectral resolution, the implementation of multivariate data analysis can be used to overcome some aspects of the decreased overall performance relative to benchtop instrumentation. The viability of portable instrumentation coupled with chemometric classification algorithms is shown across two distinct applications. First, successful classification of individual species of tropical hardwoods from the genus Dalbergia and its lookalikes are shown. In this analysis, elemental fingerprints of each hardwood are collected with laser induced breakdown spectroscopy (LIBS) under varying conditions – including low signal-to-noise (S/N) with many spectra and high S/N with fewer spectra – and distinguished with a series of classification algorithms, including Partial Least Squares Discriminant Analysis (PLS2-DA), k-Nearest Neighbors (k-NN), Classification & Regression Trees (CART), Random Forests (RF), and Support Vector Machines (SVM). It can be concluded from this study that not only is LIBS a viable handheld tool to identify wood species, but also fewer spectra of higher quality data modeled with SVM yields the best classification results. Second, historical textiles are analyzed with fiber optic reflectance spectroscopy (FORS) and x-ray fluorescence (XRF) and classified based on a flat classifier “decision rule.” The decision rule is created based on visible reflectance peaks and shows better clustering relative to other relevant wavelength ranges discussed in the art conservation literature. This cluster analysis problem shows that when dyeing textiles, chromophores are present in such small quantities that bulk properties such as textile color overwhelm any trace analysis signals. In addition, at least for textiles, XRF spectra presented in this work indicate that FORS inflection point does not correlate with elemental composition of the textile & mordant.

Geological Applications

From Mineral Sources and Stalactites to Soils and Street Safety: LIBS Applications that Improve the Quality of our Lives

Nancy J. McMillan; New Mexico State University

Laser-Induced Breakdown spectroscopy (LIBS) with chemometric analysis and AI offers potentially disruptive capabilities. Each LIBS spectrum contains an enormous amount of information, including concentrations of all naturally-occurring elements, isotopic ratios, and structural information. Several projects highlight the unique characteristics of chemometric analysis of LIBS spectra.

The geographic origin of gemstones is significant because: 1) gemstone value is in part based on provenance, and 2) agreements intended to limit human rights violations depend on accurate provenance determination. Traditional techniques comparing compositional similarities of relatively small sample sets on three-component chemical diagrams yield unsatisfactory results. Using LIBS, Kochelek et al. (2015) studied 569 rubies and sapphires from 21 locations in 11 countries with successful prediction rates of 97.9% (sapphire) and 95.4% (ruby) for the mine of origin. This approach was successful because both the number of samples and variables was large.

Identification of biotic and abiotic calcite cave formations permits of mapping the spatial distribution of not only where bacteria are currently active but also of where they were active in the past, a method potentially useful in the search for extraterrestrial life. Calcite samples from Fort Stanton Cave, New Mexico, USA, were analyzed with both desktop and handheld LIBS units; chemometric models resulted in successful prediction rates of 92% for both instruments.

Rapid measurement of key nutrients in soils could enable customization of fertilizers to provide only the nutrients missing in specific plots Omer et al. (2020) calibrated LIBS and visible-near infrared spectra to determine the concentrations of key nutrients in soils, demonstrating that LIBS provides good calibration curves.

Finally, aggregate materials used in roadways affect pavement quality. An automatic LIBS unit analyzed rock aggregate samples; chemometric analysis then pulled engineering properties from the calibrated spectra, some directly related to chemical composition. Successful models were developed to predict the specific gravity, expansion during freeze/thaw, and frictional properties of aggregates, as well as the identification of deleterious materials in aggregates. These applications illustrate the power of this technology to change the way we think about the quality and sources of materials that we consume in our everyday lives.

Contribution of LIBS to Mineral Resources: from Multi-Elementary Analysis to Mineralogical Mapping

Cécile Fabre; Universite de Lorraine / GeoRessources

Mineralogical and petrographic studies require analytical methods capable to underline the repartition of major to trace elements within geological samples. The EMPA (Electron Microprobe Analysis) and µXRF (X-Ray Fluorescence) conventional methods used for such investigation, but on restrictive zones, are on the verge to be reached by µLIBS (Laser Induced Breakdown Spectroscopy) technique allowing rapid elemental cartography on thin rock sections or even larger samples in ambient conditions. This spectroscopic method with extremely fast acquisition speed (up to 1kHz), low detection limits especially for light elements (at sub-ppm level) is perfectly adapted to perform multi-elemental imaging of major to trace elements, and the possibility to scan large surfaces (several cm2 ) with a microscopic resolution (down to 15 µm). In addition, since it is an all optical methods, it is rather easy to couple other characterization modalities such as optical, Raman or luminescence imaging. Mineral discrimination and relative elemental contents are also available with the portable LIBS tool on a millimeter observation area, directly on the surface of a rock outcrop or any rock section.

In this presentation, we will focus on recent research on the development of LIBS images for mineral resources through different topics: elemental mapping (quantitative or not), mineralogical discrimination or identification, correlation between multi-elemental results and molecular observations (i.e. Raman or luminescence) obtained with the same LIBS setup, increase of spectra acquisition (up to kHz) with an extension of the sample surface.

Indeed, if the correlation of two/three elementary maps can be completed by looking (with our eyes) at the maps, when the number of data is too important, the contribution of chemometrics techniques can be essential.

Quantitative Analysis of Fluorine in Geological Samples with Handheld Laser-Induced Breakdown Spectroscopy

Gabrielle Lambton; SciAps

Accurate, repeatable, and rapid quantitative results of fluorine obtained with a handheld LIBS analyzer.

Laser-Induced Breakdown Spectroscopy (LIBS) is a useful tool for the analysis of geological samples due to the broad range of detected elements. This study utilized a portable LIBS system for the quantification of fluorine in geological samples. Empirical calibration models were built using an advanced PC- based software, Profile Builder, to collect quantitative data. This research looks at LIBS spectra collected in both He and Ar environments. The samples used include Cu-Au ore containing 340-72,500 ppm of F. Fluorine can be difficult to detect in a LIBS spectrum due to its high excitation energy, which results in weak emission of the atomic F lines. Fluorine is common in geological samples containing Ca. During the later stages of LIBS plasma formation, F will recombine with Ca to form molecules with characteristic molecular emission bands. This study used CaF molecular bands to build an empirical calibration for F and the results were compared to a calibration built using atomic F emission lines. The accuracy and limit of detection of F improved using CaF molecular bands versus F atomic emission lines. Signal-to-background ratios improved when plasmas were formed in He compared to Ar, whereas spectral intensities increased for plasmas formed in Ar. Calibrations made from plasmas formed in He (versus Ar) provided marginally better quantitative results for F. This research presents data showing that accurate, repeatable, and rapid quantitative results of fluorine can be obtained with a handheld LIBS analyzer.

Environmental and Cultural Applications

Optimizing Hand-held LIBS Instrumentation for the Analysis of Archaeological and Historical Sites and their Environment

Vincenzo Palleschi, Bruno Cocciaro, Olga De Pascale, Giorgio Senesi; CNR, Italy

The study of archaeological and historical settlements in their natural environmental context is extremely important in the perspective of environmental archaeology, the discipline that aims to the reconstruction of ancient environments by archaeo- and paleo-botanical research. In that framework, it is essential to develop and use portable instrumentation for the analysis of the geological, biological, and archaeological materials of interest. LaserInduced Breakdown Spectroscopy (LIBS) has, in principle, all the characteristics of sensitivity and efficiency for being effectively used in this kind of studies. However, the requirement of portability reflects in poorer analytical performances of hand-held LIBS instruments with respect to their laboratory equivalent. In this talk, we will discuss the procedures that can be developed to improve the treatment of the LIBS spectra acquired with hand-held instrumentation in the study of archaeological and environmental samples.

Statistical Sorting of Commingled Remains Using Portable LIBS

Kristen Livingston, Matthieu Baudelet, Jonathan Bethard, Katie Zejdlik-Passalacqua; University of Central Florida, University of South Florida, Western Carolina University

Field-deployable LIBS technology expedites the reassociation of individuals within commingled human remains.

The commingling of human remains is a challenging situation in both forensic and archeological contexts. Skeletal elements from multiple individuals are mixed and require sorting, or reassociation, to their respective individuals. This task is often tedious if not daunting when physical and/or visual osteometric methods are employed. However, physical traits are not the only useful discriminating factor between individuals’ bones. Their chemical profile can vary from person to person as well. This study assesses whether these differences in the chemical composition of skeletal remains can uniquely classify bones into respective individual groups.

Laser-induced breakdown spectroscopy (LIBS) is the analytical method of choice to obtain such chemical profiles of bones. It requires no sample preparation and quickly renders an optical emissions spectrum that is representative of sample surface composition. Additionally, LIBS is quasi-nondestructive; there is no visible indication that material has been removed from the bone’s surface. Finally, LIBS technology is available in handheld, field-deployable instruments. As much of the work in anthropology and bioarcheology happens out in the field, portable instrumentation is critical for effective and efficient analysis.

This study simulates the analysis of mass graves and the reassociation of commingled remains based on the chemical information provided by the LIBS spectra of bones. A comprehensive data set is constructed by acquiring spectra across a large subset of bones, each from multiple known individual remains obtained at decomposition facilities. Statistical models are subsequently built and tested with supervised machine learning. In conjunction with data reduction techniques, discriminant analysis algorithms, such as LDA and PLS-DA, can successfully match an unclassified bone with the individual to whom it belongs. This technique shows promise as a tool that aids bioarcheologists and forensic anthropologists in the sorting of commingled human remains. The spectral analysis of bones 248 using portable LIBS systems has great potential to speed up the re-association of individuals within skeletal assemblages.

Poster Presentation: Application of Portable LIBS and XRF to Analysis of Archaeological Artifacts — awarded Best Student Poster

Magdalena E. Jackson, Kristen Livingston, Mary Kate Donais, Matthieu Baudelet, Jacob T. Shelley, Douglas Perrelli; Rensselaer Polytechnic Institute, University of Central Florida, St. Anselm College, State University of New York at Buffalo

Laser-induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XRF) provide rapid elemental composition of solid samples. These techniques have applications in archaeology for differentiation of similar, unidentified specimens. However, archaeology is often practiced without the use of analytical instrumentation. Elemental analysis can support archaeological digs by 126 supplementing traditional field methods with empirical information. Further, portable LIBS and XRF instruments offer the ability to perform analysis in situ and inform the direction of an excavation. In this poster, results from two archaeometry projects exploring the use of portable elemental-analysis instruments are presented.

In one case, handheld LIBS was used to analyze co-mingled human bones to organize skeletons. Error-prone and subjective methods are typically used to identify and separate co-mingled skeletal remains. It is hypothesized that LIBS can provide a viable confirmatory complementation of this process. The first step in determining the feasibility of this application was to compile a dataset of LIBS spectra from a set of distinct skeletons. Skeletal remains from Sai Island, Sudan, were used to generate samples from pre-selected bones and pre-determined sites on each bone. Over 600 measurements were collected from ten skeletons. The dataset, consisting of spectra and skeletal site information, was analyzed using pattern recognition methods to discriminate among individual skeletons. The purpose is to show that LIBS is a viable method of assigning co-mingled skeletal remains to individuals with or without reliance on sight or fit.

In another example, handheld XRF was used to examine artifacts at the excavation site of the former Cataract House Hotel in Niagara Falls, N.Y. Multiple spectra were collected from two plaster walls, which are believed to have been built during separate additions to the hotel. Analysis of XRF spectra revealed unique elemental contents, providing evidence to support this hypothesis and link plaster recipes to specific time periods. Laboratory-based XRF and LIBS measurements of these samples corroborated field results. Additional samples collected from the site included flakes of green pigment, which were analyzed using several spectroscopic methods, including XRF, Raman, and infrared spectroscopy, to reveal information about the pigment’s origin.

Advanced Approaches

Using LIBS to Characterize High Entropy Alloys for Extreme Environments

Prasoon K. Diwakar, Bharat Jasthi, Nicholas E. Pugh; South Dakota School of Mines, South Dakota School of Mines and Technology

Novel application of LIBS for high entropy alloys

Multi-principal element alloys (MPEAs) and high entropy alloys (HEAs) are a class of material that are now increasingly being used in extreme environments due to their superior properties. When operating in conditions that can cause the material to fail in unusual ways, it is important to know what is happening with the structure of the material in real-time. In this study MPEA AlNbTaTiZr was synthesized using arc melting and laser induced breakdown spectroscopy (LIBS) was used to analyze and determine various properties of the MPEA. When analyzing LIBS spectra of MPEA, presence of various lighter elements can lead to matrix effect. It is important to determine when and where a matrix effect can occur with various laser-based techniques, such as LIBS. The samples that were created and tested were either made from high-purity metals (Al, Nb, Ta, Ti, and Zr), or high purity equimolar concentrations of AlTi, AlNbTi, AlNbTiZr, and AlNbTaTiZr. It will be shown that there was a matrix effect present when titanium was added to aluminum and vise-versa but to a lesser extent when other components were added. Using the LIBS spectral analysis, various materials properties were extracted including microhardness. Further details and mechanisms of LIBS analysis MPEAs high entropy alloys will be presented.


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